The magnetic field at point P due to a 2.0-A current flowing in a long, straight, thin wire is $8.0 \mu T$. How far is point $P$ from the wire? $\left( \mu _ { 0 } = 4 \pi \times 10 ^ { - 7 } \mathrm {~T} \cdot \mathrm { m } / \mathrm { A } \right)$
A) $4.0 \mathrm {~cm}$
B) $10 \mathrm {~cm}$
C) $2.0 \mathrm {~cm}$
D) $5.0 \mathrm {~cm}$
E) $2.5 \mathrm {~cm}$

Question

Quizplus · Accepted Answer

Using the formula for the magnetic field due to a long straight wire, $ B = \frac{\mu_0 I}{2\pi r} $, and solving for $ r $, we find $ r = \frac{\mu_0 I}{2\pi B} = \frac{4\pi \times 10^{-7} \times 2.0}{2\pi \times 8.0 \times 10^{-6}} = 0.05 $ meters or 5.0 cm.

The Magnetic Field at Point P Due to a 2 8.0μT8.0 \mu T8.0μT

The Magnetic Field at Point P Due to a 2 $8.0 \mu T$